There are other factors needed in order to come up with an estimate, mainly the discount rate you'd want to apply. You can do an IRR, but you'd need a starting cost to figure it. You can use a spreadsheet and the NPV function to determine a break-even point, by assuming various initial costs. For instance, here's a table of approximate PVs with associated discount rates:

I don't understand how a discount rate fits in. What am I discounting?

For your chart values, I'm guessing there is a 0% discount rate amount?